diff --git a/backends/xnnpack/cmake/Dependencies.cmake b/backends/xnnpack/cmake/Dependencies.cmake
index d02ac4a7926..fe81f63dac9 100644
--- a/backends/xnnpack/cmake/Dependencies.cmake
+++ b/backends/xnnpack/cmake/Dependencies.cmake
@@ -76,6 +76,15 @@ set(XNNPACK_BUILD_ALL_MICROKERNELS
     OFF
     CACHE BOOL ""
 )
+
+# XNNPACK nests variadic macros (XNN_RETURN_IF_ERROR expands to xnn_log_error),
+# which MSVC's default legacy preprocessor mis-expands. Only observable where
+# XNN_LOG_LEVEL is non-zero, i.e. Debug configurations. Not applied to clang-cl,
+# which sets MSVC but already has a conforming preprocessor.
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+  add_compile_options(/Zc:preprocessor)
+endif()
+
 add_subdirectory("${XNNPACK_SOURCE_DIR}")
 include_directories(SYSTEM ${XNNPACK_INCLUDE_DIR})
 list(APPEND xnnpack_third_party XNNPACK)
diff --git a/tools/cmake/preset/llm.cmake b/tools/cmake/preset/llm.cmake
index d1b8064c342..67c9d09b794 100644
--- a/tools/cmake/preset/llm.cmake
+++ b/tools/cmake/preset/llm.cmake
@@ -20,9 +20,11 @@ set_overridable_option(EXECUTORCH_BUILD_KERNELS_OPTIMIZED ON)
 set_overridable_option(EXECUTORCH_BUILD_XNNPACK ON)
 
 # Turn on the quantized and LLM kernels unless on Windows with MSVC build since
-# they don't currently compile.
+# they don't currently compile. MSVC is also set for clang-cl, which does
+# compile them, so key off the compiler ID instead.
 if(NOT ((CMAKE_SYSTEM_NAME STREQUAL "Windows" OR CMAKE_SYSTEM_NAME STREQUAL
-                                                 "WIN32") AND MSVC)
+                                                 "WIN32")
+        AND CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
 )
   set_overridable_option(EXECUTORCH_BUILD_KERNELS_QUANTIZED ON)
   set_overridable_option(EXECUTORCH_BUILD_KERNELS_LLM ON)